Ingrown Leading to Hierarchical SAPO-34 with High Catalytic Activity

Introduce meso/macro-pore to the crystal of SAPO-34 is an efficient way to overcome its inherent diffusion resistance. Porogen, formation hierarchical structure by inhibiting the growth of the crystals, would increase the costs of SAPO-34 and is usually not friendly to environment. In this work, an ingrowth route to synthesize hierarchical SAPO-34 is developed by secondary silica addition via hydrothermal method. Hierarchical porous SAPO-34 was synthesized without adding any pore-generating agent. Secondary silica addition put off the Si and P transferring from the mother liquid to gel phase, leading to the chemical composition of surface first meeting to the crystallization conditions. Then the crystallization started from the surface to the inside of the amorphous particles. The hierarchical SAPO-34 showed numerous meso/macro pore structure and weaker acid strength. So the hierarchical SAPO-34 showed better catalytic activity than the conventional SAPO-34 in MTO reaction.